The invention relates to an induction device for an internal combustion engine in accordance with the preamble of the main claim.
Such an induction device is disclosed, for instance, in published German Application No. 39 21 081. This known induction device with an intake pipe arrangement for a multicylinder internal combustion engine has a cylindrical intake manifold chamber and individual intake pipes leading to the individual cylinders which are extended around the intake manifold chamber and are arranged side by side in longitudinal direction thereof. To obtain two different ram pipe lengths, each individual intake pipe communicates with the intake manifold chamber via two control openings spaced apart at a given angle in the circumferential wall of the intake manifold chamber.
In the intake manifold chamber of this known induction device, a tubular rotary slide valve is arranged, which has at least one control slit for each intake pipe. When the rotary slide valve is in one end position, this control slit communicates with the first opening, while the other opening is covered by the wall of the rotary slide valve. This creates a long ram tube length. If the rotary slide valve is rotated to its other end position, the first opening is covered by the wall of the rotary slide valve and the control slit communicates with the second opening, so that a short ram pipe length is obtained.
A disadvantage of this known device is that it does not permit a continuously variable adjustment of the ram pipe length. This means that an optimal performance output is possible only within two narrowly limited rotational speed ranges of the internal combustion engine. The known devices thus always relate only to length-adjustable ram induction systems.
EP 0 848 145 A2 further discloses a continuously variable adjustment of the resonance tube length in the induction system for a V-type internal combustion engine. This arrangement provides for a drum as the rotary slide valve in which the intake air enters axially and through which the air is conducted into the tangentially adjacent intake pipe. Here, the adjustable length of the effective air intake pipe is simply set by rotating the drum.
Viewed in an of it self, it is also known from . . . (still to be checked . . . ) to effect a changeover between so-called ram charging and resonance charging in the induction device.
Thus it is the object of the invention to provide an induction device that permits a continuously variable adjustment of the intake pipe geometry and can be manufactured simply with a modular construction.
This object is attained by the invention in that a modular intake pipe concept, particularly for multicylinder internal combustion engines, with the features of the characterizing portion of the main claim is advantageously realized in an induction device of the initially described type.
The intake pipe concept according to the invention relates to an induction device with a particularly advantageous changeover between resonance charging and ram charging of the intake air. Here, too, a continuously variable ram pipe adjustment and a continuously variable resonance pipe adjustment are made possible. A stepped resonance pipe cross-section adjustment can also be carried out and switched together with the ram induction system. The exemplary embodiments according to the invention make it advantageously possible to carry out all the adjustment actions with, for instance, only one common actuator. However, partial functions, e.g. resonance pipe cross-section adjustment, can also be carried out by a separate actuator.
The substantial advantages of the intake pipe concept according to the invention are particularly its modular construction, which makes the principle of the induction device suitable, e.g. for 3-, 4- or generally multi-cylinder engines. Furthermore, adjustments of the resonance or ram pipe cross section (e.g. for engines of a family with equal cylinder spacing) are made possible in simple manner by the use according to the invention of adjustment disks with smaller or greater outside diameters.
In further embodiments of the induction device according to the invention with continuously variable pipe lengths, the changeover from resonance charging to ram charging can also be carried out with a different resonance switch.
In the above-described resonance charging systems, the air consumption of the internal combustion engine is advantageously improved within a certain speed range. The reason for the improved performance with ram charging at these engine speeds is that the resonance system and the ram system are only well tuned to one another within a certain range. At other speeds, the less well tuned overall system of resonance and ram pipes causes a deterioration in performance, so that the system switches over to ram charging as described.
According to one embodiment, the changeover can be avoided in that the lengths of the resonance pipe and the ram pipe are optimally tuned to one another at any speed. A resonance charging system can then be used throughout at any operating point of the internal combustion engine. The expense of a special resonance flap is omitted here, and the performance of the engine is even improved, depending on the configuration.
With respect to the ram pipes, a long ram pipe length is more likely to be advantageous at low speeds and a short length at high engine speeds. This relationship is similar in the resonance pipes. The difference between the two pipes is the magnitude of the pipe length and the variable rate of decrease in the pipe length as the rotational speed of the engine increases.
If n is the speed of the internal combustion engine and LS and LR are the lengths of the ram pipe (LS) and the resonance pipe (LR) the following is true for the optimal pipe lengths:
LSopt=LSmaxxe2x88x92KS*(nxe2x88x92n(LSmax))
and
LRopt=LRmaxxe2x88x92KR*(nxe2x88x92n(LRmax)),
where KS and KR are constants for the ram pipes (KS) and resonance pipes (KR) and n(LSmax) and n (LRmax) are the associated rotational speeds for the maximum ram pipe length or resonance pipe length. Constants KS and KR may differ, i.e., the pipe lengths of ram pipe and resonance pipe must be decreased by different amounts when the speed increases by a certain amount.
Such resonance charging can be simply realized by a corresponding modification of the above-described illustrative embodiments. If the pipe lengths of the ram pipe and the resonance pipe were wound onto a disk, as it were, the differences in the constants KS and KR could be simply realized by different diameters of the adjustment disk.
If KR is smaller than KS, i.e. if the resonance pipe length does not change as much as the ram pipe length, the difference would be that the adjustment disks of the resonance pipes would me smaller in diameter and the housing for these pipes would be correspondingly reduced to maintain the pipe diameter. If KS were smaller than KR, the situation would be reversed, that is, the disks of the ram pipes would be smaller. In the design of the ram pipe according to one of the above-described embodiments, care must be taken that the axial friction surfaces on the adjustment disks of the ram pipe and the resonance pipe lie on the same radius even if the outside diameters of the adjustment disks differ.
In the latter embodiment, the resonance flap, i.e. the disks with apertures and possibly an iris diaphragm, and thus in principle resonance switching, can be eliminated. Instead, closed walls with a central passage for the shaft would enclose the resonance volume. The design of the intake pipe in the induction device according to the invention would otherwise remain unchanged.
In a further advantageous embodiment of the induction device according to the invention, the design of the housing of the induction device and, in particular, the internal sealing technology is advantageously improved, so that the intake pipe can be manufactured more cost effectively and modularization is promoted.
The induction device is no longer partitioned lengthwise, i.e. in the plane of the rotary axis of the adjustment disks contained in the intake pipe, but perpendicularly thereto. The surrounding housing, similarly to the inner workings, the adjustment disks, is constructed from individual disks. The normally required sealing disks are omitted. Instead, sealing lips are molded onto the adjustment disks, preferably on the exterior part of each of the two-part adjustment disks.
The sealing lips of this embodiment provide a seal between the adjustment disks and the surrounding housing wall, which projects into the intake pipe and assumes the function of the sealing disks. The adjustment disk, or only the part thereof that carries the sealing lip, need not be made of the same material as the housing. The material should take into account the requirements of the sealing lip geometry and the friction relative to the housing. The requirements for dimensional accuracy and axial runout of the adjustment disks are lower in this alternative concept.
The adjustment disks are threaded onto a shaft as before. They are no longer clamped with a spring. At least on the end faces of the housing, end disks with a shaft bearing must be provided. The actuation of the shaft to continuously vary the respective lengths of the pipes is effected as described above.
The housing disks of the latter embodiment are all identical, except for the end pieces, which may have a different design. This is also true for the adjustment disks. The modular construction of the intake pipe is thus considerably simplified. Depending on the number of cylinders of the internal combustion engine and the respective intake pipe concept, a different number of adjustment and housing disks is assembled. Depending on the concept, the individual housing or adjustment disks are all mounted in the same orientation (e.g. in an inline engine with ram charging only) or alternately rotated by, for example, 180xc2x0 (e.g. in a combination of resonance charging and ram charging). The pipe branches issuing from these housing disks should be completely located within the housing disk. Consequently, the corresponding pipe sections need not be produced by assembling two adjacent housing disks, which considerably simplifies the interconnection of the housing disks.
The housing disks can be simply interconnected by means of the tongue and groove principle. The tongue and groove geometry along the circular periphery remains unchanged. The connection may be made, for instance, as a snap connection, e.g. with a sealing ring, or by welding. Advantageously, the entire intake pipe can be preassembled and prestressed before connecting all the housing disks to the respective adjacent disks by laser welding in a single operation.
To simplify the principle and execution, the intake pipe can be separated from the ram pipe end sections facing the cylinder head, i.e. downstream from the basic intake pipe body. The ram pipe end sections and the basic body are connected, for instance, by means of rubber sleeves. A precollector as described above, if present, or the piping extending thereto, can be connected in similar manner. If no precollector is present, the inflow from the throttle valve into the interior plenum may also occur axially.
The above-described housing constructed from individual disks can be combined with all the other embodiments. The tongue and groove principle works in every case. The possibility of closing one resonance pipe per resonance header by a corresponding embodiment of the exterior resonance pipe wall formed by the housing is feasible and meaningful in this embodiment as well.
These and other features of preferred further embodiments of the invention are set forth in the claims as well as in the description and the drawings. The individual features may be implemented either alone or together in subcombinations in embodiments of the invention or in other fields of use and may represent advantageous embodiments that are protectable per se, for which protection is hereby claimed.